The slippery slope from same-sex marriage to polygamy

Via Full Marriage Equality, a great commentary on the slippery slope of same-sex marriage:

We’ve all heard it before: “If we allow gay marriage, next thing people will be trying to legalize polygamy!” Which statement will get one of two responses from pro-marriage-equality folks: “That’s ridiculous!” or “Uh… yeah?” You may guess that I’m in the latter category, and you’d be right. But then the stereotypical protester will say, “And next thing they’ll allow a man to marry a dog, or an eight-year-old!”

[...] Well, I’ll tell you: totally fallacious. And that’s because there’s a big brick wall about halfway down the slippery slope. And on that wall, in bold capital letters, are the words “CONSENTING ADULTS.” Consent is the watchword of modern sexual ethics. It’s the difference between BDSM and abuse. It’s the difference between polyamory and cheating. It’s the difference between rape and… sex. Anything two (or more) able, informed adults give consent to in private is generally considered okay. [...] There’s a little philosophical room around the question of who is able to give consent, but it’s generally understood that children, animals, and the severely mentally impaired (either permanently or temporarily, as by alcohol) are not.

[...] It’s hard to imagine what other questions can sensibly be invoked. People who argue the gay marriage -> polygamy -> pedophilia -> bestiality slippery slope are usually correlating these four very different behaviors because all of them seem “unnatural.” But “natural” and “unnatural” are subjective and mostly meaningless categories. “That’s not natural” really just means “That makes me uncomfortable.” And I hope we can all agree that an individual’s sense of comfort or discomfort makes for a really lousy moral guide. Someone might say, “But that goes against my religious code!” Fine, then don’t do that, and encourage your religious brethren not to do it either. But that has nothing to do with whether a thing should be legal or acceptable in the culture outside your religion.

[...] The question with gay marriage has been, “Is it healthy for a child to be raised by same-sex parents?” The preliminary results are in on that one, and the answer is yes. Whenever society takes up the question of polygamy, the same question will be asked, and I think that’s fair. With polygamy, there are additional questions raised, relating to things like citizenship and insurance benefits. But all these questions can and should be answered with hard evidence and studies, not on the basis of people’s gut sense of comfort or discomfort.

[...] Suppose study after study showed that children, in fact, do better when raised by same-sex parents, or polyamorous parents. (I can think of several reasons why either might be so.) How much better would it have to be before you’d support a ban on heterosexual monogamy? We’ve known for decades that children do better when raised by two parents rather than one, but no sane person suggests a law preventing single people from having children. We hold very highly the rights of heterosexual people to live, love, and create families as they see fit. In time, I hope that consenting adults of any number and gender are given the same level of respect.

The fallacy of the “animal marriage” argument has been pointed out before.

I cannot possibly stress how much I agree with this.